Adjustable damping assembly for watt-hour meters



Aug. 6, 1940. s. s. GREEN ADJUSTABLE DAMPING ASSEMBLY FOR WATT-HOUR METERS Filed Jan. 5. 1938 2 Sheets-Sheet 1 1, L 13 W 1 EE- 1940- s. s. GREEN 2.209,969

ADJUSTABLE DAMPING ASSEMBLY FOR WATT-HOUR METERS Filed Jan. 5, 1938 2 Sheets-Sheet 2 Patented Aug. 6, 1940 UNITED STATES PATENT OFFICE ADJUSTABLE DAIVIPING ASSEMBLY FOR WATT-HOUR METERS Application January 5,

6 Claims.

This invention relates to watt-hour meters and particularly to the mounting and adjustment of the damping magnets of such meters.

Applicant has previously worked out a very satisfactory form of damping adjustment as applied to old style damping magnets in which the damping flux is obtained from a pair of magnets with each magnet straddling the disc and the two magnets positioned so that their four poles are close to one another. The present invention is concerned primarily with providing equally satisfactory adjustment for a different type of damping magnet in which a single magnet is used, positioned entirely above the disc with a soft iron magnetic armature positioned below the disc. With this construction concentrated flux passes from one pole of the magnet down through the disc into the armature, and from the armature back up through the dies to the other pole of go the magnet.

Although improvements in the means of ad justment need not theoretically afiect the performance of a meter since old types of adjustment can be properly adjusted with sufiicient u care, yet from a practical standpoint the extremely convenient adjustability which applicant has worked out is very important. Meters should be adjustable from the front since the sides of the meter are often inaccessible. They should preferably be adjustable by turning about a forwardly extending axis as with a screw driver because such adjustment is the most convenient, permitting an infinitesimal turn or a full half turn or more with one movement of the wrist.

The adjustment should also be free from backlash since it is important for the convenience of testers that a given slight turn of the adjusting screw will always have the same adjusting efiect, regardless of which way the screw had previously been turned. The adjusting means should be self-locking soas not to require tightening of a locking screw, and should be capable of removal from the meter without disturbing the adjustment. The importance of these five fea- 5 tures is probably most obvious in the meter adjustment department of a factory where it is found that an operator can adjust a great many more meters a day with the combination of these five requirements than otherwise. Furthermore,

the adjustment of the meter probably averages a slightly greater degree of accuracy than with any meters in which there is backlash in the adjustment or any possibility of change after the adjustment has been made, as in the case oi tightening a set screw, for example.

1938, Serial No. 183,433

One object of the present invention is therefore to provide, for the new type of damping magnet, means of adjustment which can be adjusted by a screw-driver type of movement from the front of the meter and which is free from backlash, the adjustment being self-locking and not altered by removal of the magnet assembly from the meter. Another object of the invention is to provide an adjusting device which tends to maintain maximum flux passing through the magnet at all times so as to give the magnet the utmost protection against loss of strength, a magnet being less susceptible to weakening in iluences if the maximum flux is passing therethrough.

The problem of attaining these objects is particularly acute with the compact type of polyphase meter illustrated in which the space for the magnets and adjusting means between the two driving elements is quite limited, and both of the above mentioned objects are attained in the applicants invention by providing a shunt bar which bridges the poles of the magnet and is movable with respect thereto by a screw device free from backlash, the magnet being maintained free from play by a suitable guide means, all parts being carried by the frame. Adjustment by a shunt instead of by moving the armature below the disc assures that at all times the flux flowing through the magnet will be at least as great as the maximum which would flow through the disc to the armature and back again.

Additional objects and advantages will be apparent from the following description and from the drawings, in which:

Fig. i is a side elevation of a meter embodying this invention, the case being shown in section and many parts being omitted for the sake of clarity.

Fig. 2 is an enlarged fragmentary horizontal sectional view taken approximately on the line 2-2 of Fig. 4.

Fig. 3 is a partly sectional front view of the meter shown in Fig. 1 but with the front driving unit removed to show the arrangement of the damping magnets.

Fig. 4 is an enlarged fragmentary vertical sectional view taken approximately on the line 4-4 of Fig. 2.

Although this invention may take numerous terms, only one has been chosen for the purpose of illustration. This form is illustrated as part of a meter mechanism carried by a base plate Hi. It will be noted that the electrical connections are omitted for the sake of clarity since the present invention is not concerned with them. The meter mechanism is housed by a glass cover 11. It includes an inner or rear driving unit I 2 carried by the base plate ill, a frame l3 carried by the driving unit I2, and a front or outer driving unit 44 carried by the frame I3. The two driving units I2 and M are provided in polyphase meters, and for ordinary single phase measurements the front unit could be omitted. It will be noted that when two driving units are provided on one disc in this manner the available space for the damping unit is quite restricted.

The meter disc I9 is rotatably carried by the frame [3. Above the disc I9 is positioned a damping magnet 20 and below the disc is positioned the armature 2|. An adjusting shunt 22 bridges the poles of the magnet 20 and. is movable by suitable mechanism to be described. All of this damping assembly including the magnet 20, armature 2i, shunt 22 and adjusting mechanism is carried by the frame so that when the frame is removed there is no change in the damping magnet adjustment and when the meter has been reassembled there is no change in the meter adjustment.

It will be observed that the front unit may be removed by releasing screws IS. The frame or the frame and the front unit together may be removed from the rear unit l2 by removal of the screws I1, and the rear unit can be removed with or after the front unit It and the frame i3 by removal of the screwslB.

The shunt 22 is carried by a flange 23 which may be welded to the shunt 22 and which in turn is secured to a bracket 24 by screws 25 which pass through a slot 26 in the bracket 26 and screw into the flange 23. The bracket 24 is carried by an arm or plunger 21 having an enlarged securing portion 28 and sliding in the frame l3, thus holding the shunt 22 properly positioned with respect to the magnet 20. The entire adjusting assembly including parts 22 to 28 are slid in andout (or in a longitudinal direction with respect to shunt 22) by a screw 30 which screws through a splitcollar 32 swedged or otherwise secured to the bracket 24. The screw 30 is journaled in a split bracket 34 which is secured rigidly to the frame [3 by a screw 35. The prongs 36 of split bracket 34 ride in a slot 31 cut in screw 30. The prongs 36 are oversize with respect to the width of the slot 31 so.

that they bear firmly against the sides of this slot, thus eliminating backlash in the journaling of the screw 30 and adding suflicient fric tion so that there is no danger of the adjustment changing by vibration. The prongs 36 may be sprung into the slot 31 and may bear resiliently against the bottom of the slot if preferred, although this is not necessary.

Backlash is also eliminated at all other points where it might appear. Thus, the split collar 32 engages the threads of the screw 30 with a resilient pressure which eliminates play at that point. The arm 21 is an elongated arm which may slide a considerable distance into the frame l3 which is provided with an opening 38 reamed to fit the arm 21 snugly and extending into or through a post 39. This post 39 is also utilized for supporting the outer driving unit [4, and in fact the outer end of hole 38 may be tapped to receive screw IS. The long snug engagement of the arm 21 with the bore 38 eliminates any wabble of the adjusting assembly at this point. As a matter of fact, such wabble would be eliminated with even a reasonably snug fit due to the pull of the magnet 20 on the shunt 22, providing that the shunt 22 is spaced awayslightly from the magnet. It is also desirable that the shunt 22 be spaced away from the mag- -net for other reasons. One is so that the shunt will not strike any irregularitiy on the magnet which would oppose the adjusting movement of the shunt, and the other is so that the adjusting effect of the shunt will be smooth as the shunt is moved along throughout its range of movement. If the shunt were allowed to contact the magnet, the irregularities of the magnet surface would. cause irregularities in the adjusting efiect of the shunt as it is moved along the magnet.

It is to permit uniform and exact spacing of the shunt 22 from the magnet 20 in spite of irregularities in each magnet and variations in the sizes of different magnets that the screws 25 and slot 26 are provided. These permit the shunt 22 to be adjusted with respect to the bracket 24. This adjustment is very simple, it being merely necessary to put a flat spacer between the shunt 22 and the magnet 20 after the magnet has been rigidly secured in place. When the screws 25 are loosened the magnetism will draw the shunt 22 into engagement with the spacer, and since there is slight play between the screws 25 and the slot 26 the magnetism will also accurately aline the shunt 22 with the side of the magnet. In other words, the magnetism will twist the shunt 22 about a horizontal axis passing through one of the screws 25 until the face of the shunt 22 is drawn flat against the 35 which is enlarged as seen in Fig. 2 to form a magnet table. Between the washer 42 and the magnet 20 may be inserted a bar 44 of a material having a negative temperature coefficient of permeability to provide the usual temperature compensation for the meter. compensating bar id has been shown notched at its bridging portion at 45 to reduce the temperature compensating effect, inasmuch as very little temperature compensation is needed with the particular magnets 20 and the particular driving units l2 and is which have been chosen for illustration. It may be noted that the magnets 20 are made of a material having a very high coercive strength, the material known commercially as Alnico being preferred partly because of its very low temperature coefficient.

The armature 2| is rigidly secured by a screw 41 to the underportion 48 of frame 13. This armature may be permanently secured in position, and before the disc l9-is mounted in the frame I 3 the magnet 20 may be spaced accurately from the armature 2| by the'insertion of a spacing member therebetween before the screw 4| is tightened. The frame I3 is die cast from a nonmagnetic metal such as aluminum and therefore has no effect on the magnet? This makes it possible to mount the magnet'direc'tly on the frame as stated and also makes it possible for' the frame to extend between the poles of the magnet as seen best in Figs.2 and 4. The shunt 22 extends through an oversize hole 49 in the frame l3.

It will be observed that although the discussion has been with regard to one magnet 2!] there are two magnets 20 in the polyphase meter to give The temperature adequate damping torque. These magnets and their adjusting mechanisms are identical except for being reversed due to the fact that one is on the right-hand side and the other on the left. These two magnets, being positioned as they are between the driving units l2 and I4, serve to shield each driving unit from magnetic influences from the other. To make this shielding more complete a plate formed preferably of a magnetic metal may be shaped to fit the available space left unshielded by the magnets and secured to the frame.

It may also be noted that the frame i3 is provided with an aperture 52 into which may extend a pin for pivotally carrying a gear frame 53 which has been partly broken away in Fig. 3 for the sake of showing the main frame [3. The gear frame 53 carries a reduction gear train including gear 54 which meshes with worm 55 on the shaft of the disc IS. The mesh of gear 54 and worm 55 is preferably adjustable by means of a knurled pin 56 to which the frame 53 is eccentrically secured by a screw 51. The extension 58 of the frame l3 in which the pin 56 is journaled issplit so as to resiliently engage the pin 56 and hold it temporarily in any position to which it is set, while the screw 51 is being tightened.

A convenient order of assembly of the frame and the damping magnet assembly will be to apply the armature 2| first, then slip the magnet 20 in place, placing aspacer between it and armature 2|, and thereafter apply the screw 4! carrying the washer 42 and temperature compensating bar'44. After the screw 4| has been tightened, the spacer is withdrawn. Next, the adjusting assembly including parts 22 to 28 and also screw 30 and bracket 34 are slipped into place in the frame and secured in place by the screw 35. Thereafter, the shunt 22 is accurately spaced from the magnet 20 by a spacer, and the screws 25 are tightened. The disc l9 may now be mounted on the frame and the remainder of the meter assembled in the usual way.

The screw 30 is provided with a slotted head which is exposed on the front side of the frame and, as seen from Fig. 3, is positioned laterally beyond the outlines of the driving units (the two driving units being identical). This makes the adjusting screw 30 readily accessible with a screw driver from the front of the meter. As previously stated, all backlash is eliminated so that the greatest simplicity of adjustment is attained. Furthermore, the adjusting parts are all carried by the meter frame so that the adjustment is not destroyed when the meter frame is removed and replaced in servicing the meter.

The disclosures of this application are illustrative and the invention is not to be limited by them. In fact, if modifications or improvements are not at once obvious, they may be devised in the course of time to make additional use of the broad ideas taught and covered by this application. The claims are intended to point out novel features and not to limit the invention except as may be required by prior art.

I claim:

1. A watt-hour meter including a frame, a disc rotatably carried by the frame, a driving unit arranged to drive the disc, and damping means for retarding the disc including a generally U-shaped damping magnet positioned with its poles adjacent one face of the disc, an armature positioned adjacent the other face of the disc and opposite the poles, and means for adjusting the damping effect of the magnet including a shunt adjacent both legs of the magnet, means for movably supporting the shunt including an elongated arm sliding'snugly in an elongated aperture in the frame and carrying said shunt, and a screw journaled to the frame in a manner substantially free from backlash and adapted to screw said arm and said shunt back and forth for adjustment and operating through threads which are substantially free from backlash.

2. A damping magnet assembly for rotating discs including a non-magnetic frame, a generally U-shaped magnet rigidly secured to the frame with its poles adapted to lie adjacent to the disc, and means for adjusting the damping effect on the disc, including a bracket, a shunt secured to the bracket and a plunger supporting the bracket and sliding snugly in the frame for guiding the shunt in a movement along a path out of alinement with the plunger but lying adjacent both legs of the magnet.

3. A damping magnet assembly for rotating discs including a non-magnetic frame, a generally U-shaped magnet rigidly secured to the frame with its poles adapted to lie adjacent to the disc, and means for adjusting the damping effect on the disc including a bracket, a shunt secured to the bracket and a plunger supporting the bracket and sliding snugly in the frame for guiding the shunt in a movement along a path out of alinement with the plunger but lying adjacent both legs of the magnet, said bracket supporting the shunt slightly spaced from the magnet whereby it is drawn toward the magnet to substantially eliminate any residual play between the plunger and the frame and whereby a smooth variation of the damping effect is obtalned.

4. A damping magnet assembly for rotating discs including a non-magnetic frame, a generally U-shaped magnet rigidly secured to the frame with its poles adapted to lie adjacent to the disc, and means for adjusting the damping effect on the disc including a bracket, a shunt secured to the bracket and a plunger supporting the bracket and sliding snugly in the frame for guiding the shunt in a movement along a path out of alinement with the plunger but lying adjacent both legs of the magnet, said bracket supporting the shunt slightly spaced from the magnet whereby it is drawn toward the magnet to substantially eliminate any residual play between the plunger and the frame and whereby a smooth variation of the damping effect is obtained, the position of said shunt with respect to said bracket being adjustable to permit accurate spacing of the shunt with respect to the magnet.

5. A watt-hour meter including a driving unit, a frame secured to the driving unit, a disc rotatably carried by the frame, a generally U-shaped damping magnet secured to the frame and having two closely spaced poles adjacent one face of the disc; said frame extending between the legs of the magnet and around the edge of'the disc, an armature supported by the frame opposite the poles of the magnet and adjacent the other face of the disc, and a damping adjustment assembly including a shunt member adjacent the legs of the magnet and extending through a hole in the frame, a plunger carrying the shunt member and extending into another aperture in the frame and sliding smoothly therein, and an actuating screw for moving the shunt member and the plunger extending through a third hole in the frame.

6. A watt-hour meter including a driving unit, a frame secured to the driving unit, a disc rotatably carried by the frame, a generally U-shaped damping magnet secured to the frame and having two closely spaced poles adjacent one face of the disc; said frame extending between the legs of the magnet and around the edge of the disc, an armature supported by the frame opposite the poles of the magnet and adjacent the other face of the disc, and a damping adjustment assembly including a shunt member adjacent the legs of the magnet and extending through a hole in the frame, a plunger carrying the shunt member and extending into another aperture in the frame and sliding smoothly therein, and an actuating screw for moving the shunt member and the plunger extending through a third hole in the frame and rotatably secured substantially free from play with respect to the frame by a removably secured journal member engaging the screw with resilient pressure.

STANLEY S. GREEN. 

